Research

I am interested in the evolution of galaxies and the processes which drive that evolution. For this, I study the active phases of galaxies: mergers, starbursts, and active galactic nuclei (AGN). I am primarily an observer, but I also run and analyze N-body simulations of galaxy mergers with the aim of matching the simulations to observations. Summaries of my ongoing and recent research activity are provided below.

Dynamical Models of Galaxy Mergers

The redistribution of stars and consumption of gas by star formation and AGN during galaxy interactions and mergers have a strong influence on the properties of the galaxies involved, driving significant morphological transformation. I am matching dynamical models to observations of local mergers in order to facilitate detailed comparisons between numerical models of star formation and the actual star formation taking place in these systems. This modeling effort will accurately timestamp individual systems, something not previously available any sample of galaxy mergers.

To the left is a visualization of the gas in a simulated merger of two disk galaxies (with orbital parameters matched to NGC 2623, though the video has not been rotated to match our viewing direction).

The Interstellar Medium of Luminous Infrared Galaxies

There exist populations of galaxies where the bulk of their energy is emitted in the infrared. The "Luminous Infrared Galaxies" (LIRGs) are powered by a combination of star formation and AGN. In addition to the numerical simulations described above, I am also investigating the atomic and molecular gas properties of these systems via radio and mm observations of atomic and molecular gas tracers. These observations are being studied to understand the properties of the fuel available for star formation and AGN fueling. As part of this effort I am also performing a survey of the neutral hydrogen (H I) in U/LIRGs to obtain kinematics for the above dynamical modeling, and to determine the distribution of the atomic gas in these systems. Additionally, I am using the (1–0) transitions of molecules such as CO, HCN, and HCO+ to study the physical conditions in the gas directly associated with star formation.

Dwarf Galaxy Interactions

Little is known about interactions between dwarf galaxies, compared to more massive galaxies. However, by number, mergers between dwarfs are expected to be more frequent than mergers between massive galaxies, but it is unclear how these interactions will affect the star formation rates, stellar masses, and gas content of dwarfs. I am part of the Tiny Titans (TNT) survey of local dwarf galaxies. Our SDSS-selected sample of isolated dwarf galaxy pairs and a matched sample of non-isolated pairs and individual dwarfs is being used to study the effect of interactions and mergers on dwarf galaxies. Large-volume cosmological simulations are also being used to obtain theoretical predictions for these interactions.

Active Galactic Nuclei

While it only takes a relatively small amount of gas to fuel a supermassive black hole, the energy output can potentially affect the entire host galaxy. I am interested in the interactions between radio jets and the ambient host galaxy, as well as the broadband emission from AGN and their hosts. Studying the broadband emission can disentangle the power sources of these systems: star formation vs AGN activity.